Semiconductor device and semiconductor device manufacturing method

ABSTRACT

The object of the present invention is to efficiently dissipate heat from the upper and lower main surfaces of a semiconductor device carrying a semiconductor element. A semiconductor device ( 1 ) is provided with an insulating substrate ( 10 A), an insulating substrate ( 10 B) provided so as to face the insulating substrate ( 10 A), and a semiconductor element ( 20 ) disposed between the insulating substrate ( 10 A) and the insulating substrate ( 10 B) and having a collector electrode and an emitter electrode provided on the side opposite to that of the collector electrode. The collector electrode is electrically connected to a metal foil ( 10   ac ) provided on the insulating substrate ( 10 A), and the emitter electrode is electrically connected to the metal foil ( 10   bc ) provided on the insulating substrate ( 10 B). As a result, heat generated by the semiconductor element ( 20 ) is efficiently dissipated from the upper and lower main surfaces of the semiconductor device ( 1 ).

TECHNICAL FIELD

The present invention relates to a semiconductor device and a method for manufacturing a semiconductor device, and more particularly to a semiconductor device carrying a power semiconductor element and a method for manufacturing a semiconductor device.

BACKGROUND ART

In inverter devices, uninterrupted power supply devices, machine tools, and industrial robots, semiconductor devices (semiconductor packages), which are independent from the main device and carries a power semiconductor elements, are used.

For example, FIG. 16 is a principal view of a semiconductor deviance carrying a power semiconductor element.

As shown in the figure, in a semiconductor device 100, a parallel connection circuit is provided between a metal bar 130 a and a metal bar 130 b by bringing main electrodes of an IGBT (Insulated Gate Bipolar Transistor) element 110Na and electrodes of a diode 110Nb into contact respectively with the bars, a parallel connection circuit is provided between the metal bar 130 b and a metal bar 130 c by bringing main electrodes of an IGBT element 110Pa and electrodes of a diode 110Pb into contact respectively with the bars, the parallel connection circuits are connected respectively in series via the metal bar 130 b and sealed with a resin, and the IGBT elements, diodes, and metal bars are electrically connected by a shrinkage pressure of a sealing resin 150 (see, for example, Patent Document 1).

In the semiconductor device 100 having such a configuration, heat generated from the IGBT element 110Na and the diode 110Nb is easily conducted to a heat-dissipating fin 170N. Heat generated from the IGBT element 110Pa and the diode 110Pb is easily conducted to a heat-dissipating fin 170P. The semiconductor device 100 thus has a structure in which heat is conducted to one surface side of each heat-generating semiconductor element, and heat dissipation is facilitated.

Further, it has also been suggested to attempt heat dissipation from both the upper and lower surface sides of semiconductor elements (see, for example, Patent Documents 2 and 3).

A technique has also been known by which a semiconductor element is thermally connected to a cooling body via a thermal compound, a resin sheet, or an insulating layer formed by an aerosol deposition method (see, for example, Patent Document 4).

Patent Document 1: Japanese Patent Application Laid-open No. 2006-134990

Patent Document 2: Japanese Patent Application Laid-open No. 2004-22844

Patent Document 3: Japanese Patent Application Laid-open No. 2007-173680

Patent Document 4: Japanese Patent Application Laid-open No. 2006-165498

However, with some configurations of the conventional semiconductor devices, heat dissipation ability is insufficient and device reliability is reduced, or the increase in heat dissipation ability prevents the devices from being reduced in thickness and miniaturized.

DISCLOSURE OF THE INVENTION

With the foregoing in view, it is the object of the present invention to provide a semiconductor device in which heat generated from the semiconductor elements carried by the device can be efficiently dissipated and also to provide a method for manufacturing such a semiconductor device.

In order to solve the above-described problem, according to one aspect of the present invention, a semiconductor device includes: a first substrate comprising a first insulating plate, a first metal foil having a portion provided in a region on the inner side from the ends of a first main surface of the first insulating plate, and a second metal foil having a portion provided in a region on the inner side from the ends of a second main surface of the first insulating plate; a second substrate comprising a second insulating plate, a third metal foil having a portion provided in a region on the inner side from the end of a first main surface of the second insulating plate, and a fourth metal foil having a portion provided in a region on the inner side from ends of a second main surface of the second insulating plate, where the third metal foil is disposed so as to face the first metal foil; a semiconductor element having a first main electrode provided between the first substrate and the second substrate, and electrically connected to the first metal foil, and a second main electrode electrically connected to the third metal foil; and a sealing resin that seals the semiconductor element, wherein the sealing resin covers side surfaces and end surfaces of the first insulating plate on the outer side from the first metal foil and the second metal foil, side surfaces and end surfaces of the second insulating plate on the outer side from the third metal foil and the fourth metal foil, and side surfaces of the second metal foil and the fourth metal foil; and a main surface of the second metal foil on the side opposite to that of the first insulating plate, and a main surface of the fourth metal foil on the side opposite to that of the second insulating plate are exposed from the sealing resin.

According to one aspect of the present invention, a semiconductor device includes: a first metal plate; a second metal plate provided as to face opposite to the first metal plate; a semiconductor element disposed between the first metal plate and the second metal plate and electrically connected to the first metal plate and the second metal plate; a first deposited layer with insulating properties formed on a main surface of the first metal plate on the side opposite to that of the semiconductor element; and a second deposited layer with insulating properties formed on a main surface of the second metal plate on the side opposite to that of the semiconductor element.

According to one aspect of the present invention, a method for manufacturing a semiconductor device includes the steps of: forming a first substrate by providing the first metal foil and the second metal foil on one main surface of a first insulating plate; facing a first main electrode provided on one main surface of a first semiconductor element to the first metal foil, and electrically connecting the first main electrode and the first metal foil; facing a second main electrode provided on one main surface of a second semiconductor element to the second metal foil, and electrically connecting the second main electrode and the second metal foil; forming a second substrate by providing third and fourth metal foils on one main surface of a second insulating plate; and arranging a surface side of the second substrate where the third metal foil and the fourth metal foil are provided, so as to face a surface side of the first substrate where the first semiconductor element and the second semiconductor element are disposed, electrically connecting the third metal foil and a third main electrode provided on a main surface of the first semiconductor element on the side opposite to that of the main surface where the first main electrode is provided, and electrically connecting the fourth metal foil and a fourth main electrode provided on a main surface of the second semiconductor element on the side opposite to that of the main surface where the second main electrode is provided.

According to one aspect of the present invention, a method for manufacturing a semiconductor device includes the steps of: forming a first substrate by providing first and second metal foils on one main surface of a first insulating plate; facing a first main electrode provided on one main surface of a first semiconductor element to the first metal foil, and electrically connecting the first main electrode and the first metal foil; forming a second substrate by providing a third metal foil on one main surface of a second insulating plate; facing a second main electrode provided on one main surface of a second semiconductor element, to the third metal foil, and electrically connecting the second main electrode and the third metal foil; and arranging a surface side of the second substrate where the second semiconductor element is disposed so as to face a surface side of the first substrate where the first semiconductor element is disposed, and electrically connecting the third metal foil and a third main electrode provided on a main surface of the first semiconductor element on the side opposite to that of the main surface where the first main electrode is provided, and electrically connecting the second metal foil and a fourth main electrode provided on a main surface of the second semiconductor element on the side opposite to that of the main surface where the second main electrode is provided.

According to one aspect of the present invention, a method for manufacturing a semiconductor device includes the steps of: forming a first substrate by providing a first metal foil on one main surface of a first insulating plate; facing a first main electrode provided on one main surface of a first semiconductor element to the first metal foil and electrically connecting the first main electrode and the first metal foil; facing a second main electrode provided on one main surface of a second semiconductor element to the first metal foil and electrically connecting the second main electrode and the first metal foil; forming a second substrate by providing a second metal foil on one main surface of a second insulating plate; and arranging a surface side of the second substrate where the second metal foil is provided so as to face a surface side of the first substrate where the first and second semiconductor elements are disposed and electrically connecting by using the second metal foil, a third main electrode provided on a main surface of the first semiconductor element on the side opposite to that of the main surface where the first main electrode is provided and a fourth main electrode provided on a main surface of the second semiconductor element on the side opposite to that of the main surface where the second main electrode is provided.

According to the disclosed semiconductor device and method for manufacturing, it is possible to realize a highly reliable semiconductor device in which heat generated from the mounted semiconductor element can be efficiently dissipated to the upper and lower main surface sides of the semiconductor device.

The description mentioned above and other objects, features, and advantages of the present invention will be apparent from the description below and accompanied drawings that illustrate the preferred embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a semiconductor device according to the first embodiment.

FIG. 2 is a principal schematic view illustrating a method for manufacturing a semiconductor device according to the first embodiment (first view).

FIG. 3 is a principal schematic view illustrating a method for manufacturing a semiconductor device according to the first embodiment (second view).

FIG. 4 is a principal schematic view illustrating a method for manufacturing a semiconductor device according to the first embodiment (third view).

FIG. 5 is a principal schematic view illustrating a method for manufacturing a semiconductor device according to the first embodiment (fourth view).

FIG. 6 is a principal schematic view illustrating another method for manufacturing a semiconductor device according to the first embodiment (first view).

FIG. 7 is a principal schematic view illustrating another method for manufacturing a semiconductor device according to the first embodiment (second view).

FIG. 8 is a principal schematic view illustrating another method for manufacturing a semiconductor device according to the first embodiment (third view).

FIG. 9 is a principal cross-sectional view of a configuration example of a semiconductor device having a stacked structure.

FIG. 10 is a schematic diagram of the semiconductor device according to the second embodiment.

FIG. 11 is a schematic diagram of the semiconductor device according to the third embodiment.

FIG. 12 is an explanatory drawing illustrating an example of the insulating layer formation process using an aerosol deposition method.

FIG. 13 is an explanatory drawing illustrating another example of the insulating layer formation process using an aerosol deposition method.

FIG. 14 is a schematic diagram of the semiconductor device according to the fourth embodiment.

FIG. 15 is a schematic diagram of a semiconductor device according to the fifth embodiment.

FIG. 16 is a principal view of a semiconductor deviance carrying a power semiconductor element.

EXPLANATION OF REFERENCE SYMBOLS

-   1, 1 a, 1 b, 2, 3, 4, 5 semiconductor device -   10A, 10B insulating substrate -   10 aa, 10 ba, 10 ga insulating plate -   10 c, 10 e, 10 m, 10 n, 10 p, 71, 72 external connection electrode -   10 ab, 10 ac, 10 ad, 10 bb, 10 bc, 10 aca, 10 acb, 10 bca, 10 bcb,     10 gb metal foil -   10 ada, 10 adb insulating layer -   10 g control terminal -   11, 12, 13, 14, 15, 16 solder layer -   17 connection member -   20, 20 a, 20 b semiconductor element -   20 ae, 20 be emitter electrode -   20 g control electrode -   20 w metal wire -   30, 30 a, 30 b, 33A, 33B, 34 metal plate -   31, 32 metal block body -   40 heat-dissipating fin -   40 a flow channel -   50 sealing resin -   61, 62 nozzle -   70 structural body -   73 tie bar

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

FIG. 1 is a schematic view of a semiconductor device according to the first embodiment.

As shown in the figure, in a semiconductor device (semiconductor package) 1, an insulating substrate 10A is taken as a base body, and at least one semiconductor element 20 is mounted on the insulating substrate 10A with a lead-free solder layer 11 of a tin (SN)-silver (Ag) system being interposed therebetween.

The insulating substrate 10A is provided with an insulating plate 10 aa, a metal foil 10 ab provided on the lower surface of the insulating plate 10 aa, and metal foils 10 ac, 10 ad provided on the upper surface of the insulating plate 10 aa. The metal foil 10 ab and the metal foils 10 ac, 10 ad are selectively and respectively provided on the upper and lower surface of the insulating plate 10 aa and separated by the insulating plate 10 aa. The metal foil 10 ab provided on the lower surface of the insulating plate 10 aa includes a portion provided in a region of the insulating plate 10 aa that is on the inner side from the ends of the lower surface. Likewise, the metal foils 10 ac, 10 ad provided on the upper surface of the insulating plate 10 aa include portions provided in a region of the insulating plate 10 aa that is on the inner side from the ends of the upper surface. In the insulating substrate 10A, the metal foil 10 ab is thus provided in a predetermined region of the lower surface, and the metal foils 10 ac, 10 ad are provided in predetermined regions of the upper surface of the insulating plate 10 aa. For example, when copper (Cu) or a metal containing copper (Cu) as the main component is used for the metal foils 10 ab, 10 ac, 10 ad provided on the insulating plate 10 aa, the metal foils 10 ab, 10 ac, 10 ad can be formed on the insulating plate 10 aa, for example, by using a DCB (Direct Copper Bonding) method.

Further, in addition to the aforementioned lead-free solder of a tin (Sn)-silver (Ag) system, a lead-free solder of a tin (Sn)-antimony (Sb) system may be used as the solder material of the solder layer 11 provided between the insulating substrate 10A and the semiconductor element 20. When a lead-free solder of a tin (Sn)-antimony (Sb) system is used, a characteristic of thermal fatigue resistance can be further improved.

Further, the semiconductor element 20 is the so-called power semiconductor element and, for example, corresponds to a RC (Reverse Conducting)-IGBT element. In addition to the RC-IGBT element, for example, a usual IGBT element, a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and a FWD (Free Wheeling Diode) element may be used as the semiconductor element 20.

In the semiconductor device 1, one main electrode (for example, a collector electrode) of the semiconductor element 20 is joined to the metal foil 10 ac via the solder layer 11. A metal plate 30 that functions as a heat spreader or a lead frame is joined via a lead-free solder layer 12 to the other main electrode (for example, an emitter electrode) provided on the main surface on the side opposite to that of the main surface where the aforementioned one main electrode (for example, the collector electrode) of the semiconductor element 20 is disposed. A control electrode (not shown in the figure) of the semiconductor element 20 that is separately provided on the surface side where the other main electrode (for example, the emitter electrode) is disposed and the metal foil 10 ad are electrically connected by means of a metal wire 20 w.

Further, in the semiconductor device 1, a separate insulating substrate 10B that is a base body is disposed opposite the insulating substrate 10A.

The insulating substrate 10B is provided with an insulating plate 10 ba, a metal foil 10 bb provided on the upper surface of the insulating plate 10 ba, and a metal foil 10 bc provided on the lower surface of the insulating plate 10 ba. The metal foil 10 bb and the metal foil 10 bc are selectively and respectively provided on the upper and lower surface of the insulating plate 10 ba and separated by the insulating plate 10 ba. The metal foil 10 bb provided on the upper surface of the insulating plate 10 ba includes a portion provided in a region of the insulating plate 10 ba that is on the inner side from the ends of the upper surface. Likewise, the metal foils 10 bc provided on the lower surface of the insulating plate 10 ba includes a portion provided in a region of the insulating plate 10 ba that is on the inner side from the ends of the lower surface. In the insulating substrate 10B, the metal foil 10 bb is thus provided in a predetermined region of the upper surface, and the metal foil 10 bc is provided in a predetermined region of the lower surface of the insulating plate 10 ba. For example, when copper (Cu) or a metal containing copper (Cu) as the main component is used for the metal foils 10 bb, 10 bc provided on the insulating plate 10 ba, the metal foils 10 bb, 10 bc can be formed on the insulating plate 10 ba, for example, by using the DCB method.

The metal plate 30 disposed above the insulating substrate 10A and the metal foil 10 bc of the insulating substrate 10B are joined via a lead-free solder layer 13.

The insulating substrates 10A, 10B, metal plate 30, and semiconductor element 20 are electrically and thermally connected to each other.

Further, in the semiconductor device 1, a sealing resin 50 is provided in a gap between the insulating substrates 10A, 10B and on the side surfaces thereof with the object of protecting the insulating substrates 10A, 10B, semiconductor element 20, and metal wire 20 w. The main surfaces of the metal foils 10 ab, 10 bb provided on the sides of the insulating substrates 10A, 10B that are opposite those facing the semiconductor element 20 are exposed from the sealing resin 50 and exhibited, that is, not covered by the sealing resin 50. In the semiconductor device 1, flat surfaces are formed by the main surfaces of the metal foils 10 ab, 10 bb, and also main surfaces (surfaces along the broken lines A-B in the figure) constituted by parts of the sealing resin 50.

As shown in FIG. 1, the sealing resin 50 is formed such as to seal the semiconductor element 20 and also cover the side surfaces of the metal foil 10 ab provided on the lower surface of the insulating plate 10 aa, end surfaces of the lower surface of the insulating plate 10 aa where the metal foil 10 ab is not provided, side surfaces of the insulating plate 10 aa, end surfaces of the upper surface of the insulating plate 10 aa where the metal foils 10 ac, 10 ad are not provided, and also side surfaces and upper surfaces of the metal foils 10 ac, 10 ad. Likewise, the sealing resin 50 covers the side surfaces of the metal foil 10 bb provided on the upper surface of the insulating plate 10 ba, end surfaces of the upper surface of the insulating plate 10 ba where the metal foil 10 bb is not provided, side surfaces of the insulating plate 10 ba, end surfaces of the lower surface of the insulating plate 10 ba where the metal foil 10 bc is not provided, and side surfaces and lower surface of the metal foil 10 bc.

Thus, the sealing resin 50 is formed such as to cover the steps formed by the insulating plate 10 aa and the metal foils 10 ab, 10 ac, 10 ad in the end portions of the insulating substrate 10A and also to cover the steps formed by the insulating plate 10 ba and the metal foils 10 bb, 10 bc in the end portions of the insulating substrate 10B. As a result, the bonding area of the sealing resin 50 and the end portions of the insulating substrates 10A, 10B increases over that in the case in which such steps have not been formed, that is, the case in which the side surface positions of the insulating plates and metal foils are mated. Therefore, bonding ability of the insulating substrates 10A, 10B, and the sealing resin 50 can be increased. In particular, when a ceramic material containing oxygen, for example such as alumina (Al₂O₃), is used for the insulating plates 10 aa, 10 ba, the oxygen of the insulating plates 10 aa, 10 ba contributes to the bonding with the sealing resin 50 and bonding ability can be further increased.

Further, where steps are thus formed by the insulating plate 10 aa and metal foils 10 ab, 10 ac, 10 ad at the end portions of the insulating substrate 10A, a creepage distance between the metal foil 10 ab of the lower surface and the metal foils 10 ac, 10 ad of the upper surface becomes larger than in the case in which the side surface positions of the insulating plate and metal foils are mated and no step is formed. As a result, insulating ability thereof is increased. Likewise, where steps are thus formed by the insulating plate 10 ba and metal foils 10 bb, 10 bc at the end portions of the insulating substrate 10B, a creepage distance between the metal foil 10 bb of the upper surface and the metal foil 10 bc of the lower surface becomes larger than in the case in which no step is formed. As a result, insulating ability thereof is increased. Further, since the end portions of the insulating substrates 10A, 10B where such a step is present is covered by the sealing resin 50, the insulating ability is further improved.

Further, in the semiconductor device 1, a heat-dissipating fin 40 is thermally connected via a connection member 17 to the metal foil 10 ab provided in the insulating substrate 10A. Further, a heat-dissipating fin 40 is also thermally connected via a connection member 17 to the metal foil 10 bb provided in the insulating substrate 10B. In this case, for example, a conductive compound, a lead-free solder material of a tin (Sn)-silver (Ag) system, or a solder material of a tin (Sn)-lead (Pb) system can be used for the connection member 17. The connection member 17 can be formed over the entire flat surface along the broken line A-B, and also can be formed selectively, for example, between the metal foil 10 ab and the heat-dissipating fin 40 and between the metal foil 10 bb and the heat-dissipating fin 40. When a solder material is used for the connection member 17, the metal foils 10 ab, 10 bb, and heat-dissipating fins 40 can be strongly joined by via the solder material to perform reflow processing.

The heat-dissipating fin 40 may be of a water-cooled system in which a liquid such as water is caused to flow as a coolant in a flow channel 40 a, or of an air-cooled system in which a gas such as air is caused to flow as the coolant. If necessary, the heat-dissipating fins 40 may be directly, that is, not via the connection members 17, joined by pressurization to the metal foils 10 ab, 10 bb, by clamping from the outside.

For example, a ceramic material containing at least any one of silicon nitride (SiN), alumina (Al₂O₃), and aluminum nitride (AlN) can be used for the above-described insulating plates 10 aa, 10 ba.

For example, copper (Cu) or a metal containing copper (Cu) as the main component can be used for the metal foils 10 ab, 10 ac, 10 ad, 10 bb, and 10 bc.

For example, a material containing copper (Cu), or aluminum (Al), or alloys thereof as the main component can be also used for heat-dissipating fin 40.

For example, aluminum (Al) and gold (Au) can be used for the metal wire 20 w.

For example, any of silicone gel, an epoxy resin, a cyanate resin, and a silicone resin can be used as the sealing resin 50. If necessary, a filler material constituted by an inorganic material (boron nitride (BN), aluminum nitride (AlN), and silicon nitride (SiN)) may be contained in the resin.

The thickness of the insulating plates 10 aa, 10 ba is 0.2 mm to 0.7 mm, and the thickness of the metal foils 10 ab, 10 ac, 10 ad, 10 bb, and 10 bc is 0.2 mm to 1.0 mm.

Where such thin insulating substrates 10A, 10B are provided above and below the semiconductor element 20, and the components are connected, heat generated from the semiconductor element 20 can be efficiently conducted from the upper and lower main surfaces of the semiconductor element 20 to the upper and lower heat-dissipating fins 40 via the insulating substrate 10A and the insulating substrate 10B.

Thus, the semiconductor device 1 has good electrical connection to the metal foil 10 ac provided on the insulating substrate 10A and to the metal foil 10 bc provided on the insulating substrate 10B in the upper and lower main electrodes of the semiconductor element 20. At the same time, heat generated from the semiconductor element 20 can be efficiently conducted from the upper and lower main surfaces of the semiconductor element 20 to the upper and lower heat-emitting fins 40 via the insulating substrate 10A and the insulating substrate 10B. As a result, reliability of the semiconductor device 1 can be increased.

A method for assembling (manufacturing) a semiconductor device will be described below in greater detail by taking a semiconductor device of the so-called 2 in 1 structure (a package in which two element are carried in one package) by way of example. FIGS. 2(A) to 7(C) below illustrate an example in which one arm of an inverter circuit is manufactured, but this example is not particularly limiting. Further, a solder layer introduced between the members is herein omitted in the figures, but this layer can be formed by performing the so-called reflow processing on a paste-like or a sheet-like solder material. By forming such a solder layer, it is possible to ensure electrical connection between the members.

FIGS. 2(A), 2(B), and 2(C) are a principal schematic view illustrating a method for manufacturing a semiconductor device according to the first embodiment. FIG. 2(A) is a principal plan view of a portion of the semiconductor device. FIG. 2(B) is a cross-sectional cut-out view taken along X1-Y1 in FIG. 2(A). FIG. 2(C) is a cross-sectional cut-out view taken along X2-Y2 in FIG. 2(A).

As shown in the figure, the insulating substrate 10A is formed by disposing the metal foil 10 ab on the lower surface of the insulating plate 10 aa, for example, by the DCB method, and disposing the metal foils 10 aca, 10 acb, 10 ad on the upper surface of the insulating plate 10 aa, for example, by the DCB method. Parts of the metal foils 10 aca, 10 acb protrudes from the end of the insulating plate 10 aa.

Contact electrodes located on the lower surface of the semiconductor elements 20 a, 20 b that are RC-IGBT elements are joined to the metal foils 10 aca, 10 acb, respectively, via the solder layer 11.

A metal plate 30 a, which functions as a lead frame, is joined via the solder layer 12 to an emitter electrode 20 ae, which is provided on the upper surface side of the semiconductor element 20 a. A metal plate 30 b, which functions as a lead frame, is joined via the solder layer 12 to an emitter electrode 20 be, which is provided on the upper surface side of the semiconductor element 20 b.

Control electrodes 20 g of the semiconductor elements 20 a, 20 b and the metal foil 10 ad are electrically connected by means of a metal wire 20 w.

As shown in FIG. 2(A), the metal plate 30 a joined to the emitter electrode 20 ae of the semiconductor element 20 a is extended from the emitter electrode 20 ae towards the semiconductor element 20 b, and the end portion of the metal plate 30 a is electrically connected to the metal foil 10 acb. The electrical connection of the end portion and the metal foil 10 acb can be performed by soldering, ultrasonic joining, or laser welding.

The heights (for example, height above the main surface of the insulating plate 10 aa) of the metal plates 30 a, 30 b joined to the emitter electrodes 20 ae, 20 be are preferably adjusted to the same value.

An external connection terminal 10 p serving as a positive electrode input terminal is electrically connected to the portion of the metal foil 10 aca that extends from the insulating plate 10 aa. Further, an external connection terminal 10 m serving as an AC output terminal is electrically connected to a portion of the metal foil 10 acb that extends from the insulating plate 10 aa.

A plurality of control terminals 10 g is electrically and respectively connected to a plurality of metal foils 10 ad provided on the insulating plate 10 aa, and the control terminals 10 g and the control electrodes 20 g are electrically connected to each other by the metal wire 20 w and the metal foil 10 ad.

The external connection terminals 10 p, 10 m, metal foils 10 aca, 10 acb, control terminal 10 g, and the metal foil 10 ad can be electrically connected by any method such as laser welding, soldering, ultrasonic joining, and direct joining by heating under pressure.

According to the above-described method, the control terminals 10 g are connected to the metal foil 10 ad by forming the insulating substrate 10A, soldering by the solder layer 11 of the semiconductor elements 20 a, 20 b, soldering by the solder layer 12 of the metal plates 30 a, 30 b, and then electrically connecting the control electrode 20 g and the metal foil 10 ad, and electrically connecting the external connection terminals 10 p, 10 m and the metal foils 10 aca, 10 acb. Where the control terminals 10 g are thus attached at a later stage of the process, thermal history of the control terminals 10 g in the semiconductor device formation process can be shortened.

For example, when a terminal-integrated lead frame is used that is formed by punching the control terminals, the soldering of semiconductor elements and meal plates is conducted to such terminal-integrated lead frame. However, in this case, the terminal portion of the lead frame is also exposed to heat during soldering. Therefore, as the terminals are miniaturized, the terminals can be easily deformed by heat. Such deformation of the terminals can cause various inconveniences; for example, making it impossible to insert the terminals into predetermined holes provided in the wiring substrate or connecting the terminals to the predetermined positions on the wiring substrate.

By contrast, where the control terminals 10 g are attached at a later stage, as described herein above, thermal history of the control terminals 10 g can be shortened by comparison with the case in which a terminal-integrated lead frame is used and the deformation of the control terminals 10 g by heat can be effectively inhibited. Further, since such an attachment of the control terminals 10 g at a later stage makes it possible to inhibit the deformation of the control terminals, the control terminals 10 g can be easily miniaturized, and a pitch between the control terminals 10 g can be easily reduced.

In this way, a first unit is prepared by being provided with the insulating substrate 10A having metal foils 10 aca, 10 acb provided thereon, the semiconductor element 20 a in which a collector electrode is joined to the metal foil 10 aca, the semiconductor element 20 b in which a collector electrode is joined to the metal foil 10 acb, and the external connection terminals 10 p, 10 m.

FIGS. 3(A), 3(B), and 3(C) are a principal schematic diagram illustrating a method for manufacturing a semiconductor device according to the first embodiment. FIG. 3(A) is a principal plan view of a portion of the semiconductor device. FIG. 3(B) is a cross-sectional cut-out view taken along X3-Y3 in FIG. 3(A). FIG. 3(C) is a cross-sectional cut-out view taken along X4-Y4 in FIG. 3(A).

First, the insulating substrate 10B is formed by disposing the metal foil 10 bb on the upper surface of the insulating plate 10 ba, for example, by the DCB method, and disposing the metal foils 10 bca, 10 bcb on the lower surface of the insulating plate 10 ba, for example, by the DCB method. A part of the metal foil 10 bcb protrudes from the end of the insulating plate 10 ba.

An external connection terminal 10 n serving as a negative electrode input terminal is electrically connected to the portion of the metal foil 10 bcb that extends from the insulating plate 10 ba. The external connection terminal 10 n and metal foil 10 bcb can be electrically connected by any method such as laser welding, soldering, ultrasonic joining, and direct joining by heating under pressure.

A second unit is thus prepared that has the insulating substrate 10B having metal foils 10 bca, 10 bcb provided thereon and the external connection terminal 10 n.

FIGS. 4(A), 4(B), and 4(C) are a principal schematic diagram illustrating a method for manufacturing a semiconductor device according to the first embodiment. FIG. 4(A) is a principal plan view of a portion of the semiconductor device. FIG. 4(B) is a cross-sectional cut-out view taken along X5-Y5 in FIG. 4(A). FIG. 4(C) is a cross-sectional cut-out view taken along X6-Y6 in FIG. 4(A).

First, one main surface of the first unit shown by way of example in FIGS. 2(A) to 2(C) and one main surface of the second unit shown by way of example in FIGS. 3(A) to 3(C) are disposed opposite to each other and aligned so that the metal plates 30 a, 30 b and the metal foils 10 bca, 10 bcb are opposite to each other. The metal plate 30 a and the metal foil 10 bca, and also the metal plate 30 b and the metal foil 10 bcb are joined together via the solder layer 13.

As a result, a state is assumed in which a collector electrode of the semiconductor element 20 a is electrically connected to an emitter electrode 20 ae provided on the side opposite to the collector electrode, and a collector electrode of the semiconductor element 20 b is electrically connected to an emitter electrode 20 be provided on the side opposite to the collector electrode.

Thus, the emitter electrode 20 ae of the semiconductor element 20 a and the collector electrode of the semiconductor element 20 b are connected in series by the metal plate 30 a and the metal foil 10 acb. Further, the external connection terminal 10 p serving as a positive electrode input terminal is electrically connected via the metal foil 10 aca to the collector electrode of the semiconductor element 20 a, and the external connection terminal 10 n serving as a negative electrode input terminal is electrically connected via the metal foil 10 bcb to an emitter electrode 20 be of the semiconductor element 20 b. The external connection terminal 10 m serving as an AC output terminal is electrically connected via the metal foil 10 acb to an intermediate node in which the emitter electrode 20 ae of the semiconductor element 20 a and the collector electrode of the semiconductor element 20 b are connected in series.

The insulating substrates 10A, 10B, metal plates 30 a, 30 b, and semiconductor elements 20 a, 20 b are thus electrically connected and also thermally connected.

FIGS. 5(A), 5(B), and 5(C) are a principal schematic view illustrating a method for manufacturing a semiconductor device according to the first embodiment. FIG. 5(A) is a principal plan view of a portion of the semiconductor device. FIG. 5(B) is a cross-sectional cut-out view taken along X7-Y7 in FIG. 5(A). FIG. 5(C) is a cross-sectional cut-out view taken along X8-Y8 in FIG. 5(A).

The sealing resin 50 is provided in the gap between the insulating substrates 10A, 10B and on the side surfaces of the insulating substrates with the object of protecting the insulating substrates 10A, 10B, semiconductor elements 20 a, 20 b, and metal wire 20 w.

In this case, the sealing resin 50 is provided such that the main surface of the metal foil 10 ab provided on the insulating substrate 10A and the main surface of the metal foil 10 bb provided on the insulating substrate 10B are exposed from the sealing resin 50 and exhibited.

For example, the basic structure of a semiconductor device 1 a having a 2 in 1 structure is completed by such a manufacturing method. Heat-dissipating fin 40 is then thermally connected via a solder material or an electrically conductive compound to the main surface of the metal foils 10 ab, 10 bb of the semiconductor device 1 a.

The semiconductor device 1 having a 2 in 1 structure can be also formed by another assembling method (manufacturing method). This other assembling method will be explained below.

FIGS. 6(A) and 6(B) are a principal schematic view illustrating another method for manufacturing a semiconductor device according to the first embodiment. FIG. 6(A) and FIG. 6(B) are principal plan views of portions of the semiconductor device.

As shown in FIG. 6(A), a collector electrode of the semiconductor element 20 a is joined via the solder layer 11 to the metal foil 10 aca of the insulating substrate 10A. Further, the metal plate 30 a functioning as a heat spreader is joined via the solder layer 12 to the emitter electrode 20 ae on the upper surface side of the semiconductor element 20 a.

Parts of the metal foils 10 aca, 10 acb of the insulating substrate 10A protrude from the end of the insulating plate 10 aa.

The control electrode 20 g of the semiconductor element 20 a and the metal foil 10 ad of the insulating substrate 10A are electrically connected via the metal wire 20 w.

The external connection terminal 10 p serving as a positive electrode input terminal is electrically connected to the portion of the metal foil 10 aca that protrudes from the insulating plate 10 aa. The external connection terminal 10 n serving as a negative electrode input terminal is electrically connected to the portion of the metal foil 10 acb that protrudes from the insulating plate 10 aa.

Each of the plurality of control terminals 10 g is electrically connected to a respective metal foil from the plurality of metal foils 10 ad of the insulating substrate 10A. As a result, the control terminals 10 g and the control electrodes 20 g are electrically connected via the metal wire 20 w and the metal foil 10 ad.

The external connection terminals 10 p, 10 n and the metal foils 10 aca, 10 acb and also the control terminals 10 g and the metal foil 10 ad can be electrically connected by any method such as laser welding, soldering, ultrasonic joining, and direct joining by heating under pressure.

A first unit is thus prepared that has the insulating substrate 10A provided with the metal foils 10 aca, 10 acb, the semiconductor element 20 a joined by the collector electrode to the metal foil 10 aca, and the external connection terminals 10 p, 10 n.

As shown in FIG. 6(B), the collector electrode of the semiconductor element 20 b is joined via the solder layer 11 to a portion of the metal foil 10 bc of the insulating substrate 10B. Further, the metal plate 30 b functioning as a heat spreader is joined via the solder layer 12 to the emitter electrode 20 be on the upper surface side of the semiconductor element 20 b.

The metal foil 10 bc of the insulating substrate 10B protrudes from the end of the insulating plate 10 ba.

The control electrode 20 g of the semiconductor element 20 b and the metal foil 10 ad of the insulating substrate 10B are electrically connected via the metal wire 20 w.

The external connection terminal 10 m serving as an AC output terminal is electrically connected to the portion of the metal foil 10 bc that protrudes from the insulating plate 10 ba.

Each of the plurality of control terminals 10 g is electrically connected to a respective metal foil from the plurality of metal foils 10 ad of the insulating substrate 10B. As a result, the control terminals 10 g and the control electrodes 20 g are electrically connected via the metal wire 20 w and the metal foil 10 ad.

The external connection terminal 10 m and the metal foil 10 bc and also the control terminals 10 g and the metal foil 10 ad can be electrically connected by any method such as laser welding, soldering, ultrasonic joining, and direct joining by heating under pressure.

A second unit is thus prepared that has the insulating substrate 10B provided with the metal foil 10 bc, the semiconductor element 20 b joined by the collector electrode to the metal foil 10 bc, and the external connection terminal 10 m.

FIGS. 7(A), 7(B), and 7(C) are a principal schematic view illustrating another method for manufacturing a semiconductor device according to the first embodiment. FIG. 7(A) is a principal plan view of a portion of the semiconductor device. FIG. 7(B) is a cross-sectional cut-out view taken along X9-Y9 in FIG. 7(A). FIG. 7(C) is a cross-sectional cut-out view taken along X10-Y10 in FIG. 7(A).

First, one main surface of the first unit shown by way of example in FIG. 6(A) and one main surface of the second unit shown by way of example in FIG. 6(B) are disposed opposite to each other and aligned so that the metal plates 30 a, 30 b and the metal foils 10 bc, 10 acb are opposite to each other. The metal plate 30 a and the metal foil 10 bc, and also the metal plate 30 b and the metal foil 10 acb are joined together via the solder layer 13.

As a result, the metal foil 10 bc and the emitter electrode 20 ae provided on the side of the semiconductor element 20 a that is opposite to that of the collector electrode, and also the metal foil 10 acb and the emitter electrode 20 be provided on the side of the semiconductor element 20 b that is opposite to that of the collector electrode of are electrically connected to each other via the metal plates 30 a, 30 b.

Thus, the emitter electrode 20 ae of the semiconductor element 20 a and the collector electrode of the semiconductor element 20 b are connected in series by means of the metal foil 10 bc. Further, the external connection terminal 10 p serving as a positive electrode input terminal is electrically connected to the collector electrode of the semiconductor element 20 a, and the external connection terminal 10 n serving as a negative electrode input terminal is electrically connected to the emitter electrode 20 be of the semiconductor element 20 b. The external connection terminal 10 m serving as an AC output terminal is electrically connected via the metal foil 10 bc to an intermediate node in which the emitter electrode 20 ae of the semiconductor element 20 a and the collector electrode of the semiconductor element 20 b are connected in series.

The insulating substrates 10A, 10B, metal plates 30 a, 30 b, and semiconductor elements 20 a, 20 b are thus electrically connected and also thermally connected.

Then, similarly to the configuration shown by way of example in FIGS. 5(A) to 5(C), the sealing resin 50 is provided in the gap between the insulating substrates 10A, 10B and on the side surfaces of the insulating substrates with the object of protecting the insulating substrates 10A, 10B, semiconductor elements 20 a, 20 b, and metal wire 20 w.

In this case, the sealing resin 50 is provided such that the main surface of the metal foil 10 ab provided on the insulating substrate 10A and the main surface of the metal foil 10 bb provided on the insulating substrate 10B are exposed from the sealing resin 50 and exhibited.

The basic structure of a semiconductor device having a 2 in 1 structure is completed by such a manufacturing method. The heat-dissipating fins 40 are then thermally connected via solder materials or electrically conductive compounds to the main surfaces of the metal foils 10 ab, 10 bb. Alternatively, the heat dissipating fins 40 are directly joined to the main surfaces of the metal foils 10 ab, 10 bb.

In the embodiment illustrated by FIGS. 2(A) to 7(C), RC-IGBT elements are applied to two semiconductor elements 20 a, 20 b and main electrodes of different types of these RC-IGBT elements are connected in series, but a semiconductor device in which main electrodes of the same kind are connected in parallel can be also manufactured.

For example, FIG. 8 is a principal schematic view illustrating another method for manufacturing a semiconductor device according to the first embodiment.

In the basic structure of the semiconductor device, the semiconductor elements 20 a, 20 b are joined via the solder layer 11 to the metal foil 10 ac of the insulating substrate 10A, and the collector electrodes of the semiconductor elements 20 a, 20 b are electrically connected to each other by means of the metal foil 10 ac. The metal plate 30 is joined via the solder layer 12 to the emitter electrodes 20 ae, 20 be of the semiconductor elements 20 a, 20 b, and the emitter electrodes 20 ae, 20 be of the semiconductor elements 20 a, 20 b are electrically connected to each other via the metal plate 30. The metal foil 10 bc of the insulating substrate 10B is joined to the metal plate 30 via the solder layer 13. Further, the external connection terminals 10 c, 10 e are electrically connected to the metal foils 10 ac, 10 bc, respectively. The basic structure of such semiconductor device can be assembled, for example, in the following manner.

For example, a unit is prepared that has the insulating substrate 10A provided with the metal foil 10 ac, the semiconductor element 20 a that is joined by the collector electrode to the metal foil 10 ac via the solder layer 11, the semiconductor element 20 b that is joined by the collector electrode to the metal foil 10 ac via the solder layer 11, and the metal plate 30 that ensures electrical continuity between the emitter electrode 20 ae provided on the side of the semiconductor element 20 a that is opposite to the collector electrode and the emitter electrode 20 be provided on the side of the semiconductor element 20 b that is opposite to the collector electrode, and the insulating substrate 10B provided with the metal foil 10 bc is disposed opposite to the unit. The metal foil 10 bc and the metal plate 30 are then joined via the solder layer 13.

Thus, the basic structure of the semiconductor device shown by way of example in FIG. 8 is provided with the insulating substrate 10A; the insulating substrate 10B provided so as to face the insulating substrate 10A; the semiconductor element 20 a, which is disposed in the gap between the insulating substrate 10A and the insulating substrate 10B, having the collector electrode and the emitter electrode 20 ae provided on the side opposite to that of the collector electrode; and the semiconductor element 20 b having the collector electrode and the emitter electrode 20 be provided on the side opposite to that of the collector electrode. The collector electrode of the semiconductor element 20 a and the collector electrode of the semiconductor element 20 b are electrically connected via the metal foil 10 ac provided on the insulating substrate 10A, and the emitter electrode 20 ae and the emitter electrode 20 be are electrically connected via the metal plate 30 joined to the metal foil 10 bc of the insulating substrate 10B.

By using such a basic structure, it is also possible to manufacture a semiconductor device in which main electrodes of the same kind are connected in parallel.

Further, in the case of parallel connection, the semiconductor element 20 a may be an IGBT element and the semiconductor element 20 b may be a FWD element. In this case, the collector electrode of the semiconductor element 20 a, which is the IGBT element, and the cathode electrode of the semiconductor element 20 b, which is the FWD element, are electrically connected by means of the metal foil 10 ac. The emitter electrode of the semiconductor element 20 a, which is the IGBT element, and the anode electrode of the semiconductor element 20 b, which is the FWD element, are electrically connected by means of the metal plate 30.

In this case, an example is considered in which a plurality of identical or different semiconductor elements are mounted, but it goes without saying that a semiconductor device may be constituted by mounting one semiconductor element of any kind.

If necessary, a plurality of semiconductor devices 1 obtained in the above-described manner may be stacked with the heat-dissipating fins 40 being interposed therebetween.

FIG. 9 is a principal cross-sectional view of a configuration example of a semiconductor device having a stacked structure.

FIG. 9 shows a semiconductor device 1 b of a 6 in 1 structure in which semiconductor devices 1 a having a 2 in 1 structure such as shown in FIGS. 6(A) and 6(B) are stacked, with the heat-dissipating fins 40 being interposed therebetween. FIG. 9 shows an example of a cross section corresponding to the X7-Y7 cross section in FIGS. 6(A) and 6(B).

In this case, a lead-free solder layer of a tin (Sn)-silver (Ag) system, a lead-containing solder layer of a tin (Sn)-lead (Pb) system, or an electrically conducive compound can be used as the connection member 17 that thermally connects the semiconductor devices 1 a and heat-dissipating fins 40. The connection member 17 can be formed to a thickness of 100 μm to 300 μm. Further, heat-dissipating fins 40 can be also directly joined to each semiconductor device 1 a rather than via the connection member 17.

For example, an inverter circuit device of a 6 in 1 structure can be easily formed by stacking three semiconductor devices 1 a of a 2 in 1 structure with the heat-dissipating fins 40 being interposed therebetween.

A plurality of semiconductor devices 1 such as shown in FIG. 1 and the semiconductor devices obtained from the basic structures such as shown by way of example in FIGS. 7(A) to 7(C) and 8 can be also stacked with the heat-dissipating fins 40 being interposed therebetween, in the same manner as in the example shown in FIG. 9. Further, a plurality of semiconductor devices of the same structure can be stacked, with the heat-dissipating fins 40 being interposed therebetween, and also semiconductor devices of different structures that require heat dissipation can be also stacked with the heat-dissipating fins 40 being interposed therebetween.

As described hereinabove, the semiconductor device according to the first embodiment is provided with the insulating substrate 10A, the insulating substrate 10B provided so as to face the insulating substrate 10A, and at least one semiconductor element 20 disposed in the gap between the insulating substrate 10A and the insulating substrate 10B and having a main electrode and another main electrode provided on the side opposite to that of the main electrode. The main electrode is electrically connected to at least one metal foil 10 ac provided at the insulating substrate 10A, and the other main electrode is electrically connected to at least one metal foil 10 bc provided at the insulating substrate 10B.

With such a semiconductor device, good electrical connection can be realized on the upper and lower main surfaces of the mounted semiconductor elements, and heat dissipation can be efficiently conducted from the upper and lower main surfaces of the semiconductor element and also from the upper and lower main surfaces of the semiconductor device where the semiconductor elements have been mounted. Therefore, a highly reliable semiconductor device can be realized.

Further, by disposing the thin insulating substrates 10A, 10B opposite to each other, it is possible to reduce the semiconductor device in thickness and miniaturize the device.

Second Embodiment

FIG. 10 is a schematic drawing illustrating a semiconductor device according to the second embodiment.

As shown in the figure, in a semiconductor device (semiconductor package) 2, an insulating substrate 10A is used as a base body and a metal block body 31 is mounted on the insulating substrate 10A. At least one semiconductor element 20 is mounted on the metal block body 31.

In this case, the insulating substrate 10A is provided with an insulating plate 10 aa, a metal foil 10 ab provide on the lower surface of the insulating plate 10 aa, and metal foils 10 ac, 10 ad provided on the upper surface of the insulating plate 10 aa. The metal foil 10 ab and the metal foils 10 ac, 10 ad are selectively provided in respective predetermined regions on the upper and lower surfaces of the insulating plate 10 aa and are thus separated by the insulating plate 10 aa. The metal foils 10 ab, 10 ac, and 10 ad can be formed using, for example, the DCB method.

Further, the semiconductor element 20 is the so-called power semiconductor element and, for example, corresponds to a RC-IGBT element. In addition to the RC-IGBT element, for example, a usual IGBT element, a power MOSFET, and a FWD element can be disposed as the semiconductor element 20.

In the semiconductor device 2, the metal block body 31 is joined via a lead-free solder layer 14 to the metal foil 10 ac provided on the insulating substrate 10A. One main electrode (for example, a collector electrode) of the semiconductor element 20 is joined via a solder layer 11 to the metal block body 31. A metal plate 30 that functions as a heat spreader or a lead frame is joined via a lead-free solder layer 12 to the other main electrode (for example, an emitter electrode) provided on the main surface on the side opposite to that of the main surface where the aforementioned one main electrode (for example, the collector electrode) of the semiconductor element 20 is disposed. A control electrode (not shown in the figure) of the semiconductor element 20 that is separately provided on the surface side where the other main electrode (for example, the emitter electrode is disposed) and the metal foil 10 ad provided together with the metal foil 10 ac on the insulating plate 10 aa are electrically connected by means of a metal wire 20 w.

Further, in the semiconductor device 2, a separate insulating substrate 10B that is a base body is disposed opposite to the insulating substrate 10A.

The insulating substrate 10B is provided with an insulating plate 10 ba, a metal foil 10 bb provided on the upper surface of the insulating plate 10 ba, and a metal foil 10 bc provided on the lower surface of the insulating plate 10 ba. The metal foil 10 bb and the metal foil 10 bc are selectively and respectively provided on the upper and lower surface of the insulating plate 10 ba and separated by the insulating plate 10 ba. The metal foils 10 bb and 10 bc can be formed using, for example, the DCB method.

In the semiconductor device 2, a metal block body 32 is joined via a lead-free solder layer 15 to the metal foil 10 bc provided on the insulating substrate 10B. The metal plate 30 and the metal block body 32 are joined via a lead-free solder layer 13.

The insulating substrates 10A, 10B, metal plate 30, metal block bodies 31, 32, and semiconductor element 20 are electrically and thermally connected to each other.

Further, in the semiconductor device 2, a sealing resin 50 is provided in a gap between the insulating substrates 10A, 10B and on the side surfaces thereof with the object of protecting the insulating substrates 10A, 10B, semiconductor element 20, and metal wire 20 w. The main surfaces of the metal foils 10 ab, 10 bb provided on the sides of the insulating substrates 10A, 10B that are opposite to the sides facing the semiconductor element 20 are exposed from the sealing resin 50 and exhibited, that is, not covered by the sealing resin 50. In the semiconductor device 2, flat surfaces are formed by the main surfaces of the metal foils 10 ab, 10 bb and also main surfaces (surfaces along the broken lines A-B in the figure) constituted by parts of the sealing resin 50.

Further, in the semiconductor device 2, a heat-dissipating fin 40 is thermally connected via a connection member (not shown in the FIG. 17 to the metal foil 10 ab provided on the insulating substrate 10A. Further, a heat-dissipating fin 40 is also thermally connected via the connection member 17 to the metal foil 10 bb provided on the insulating substrate 10B. In this case, for example, a conductive compound, a lead-free solder material of a tin (Sn)-silver (Ag) system, or a solder material of a tin (Sn)-lead (Pb) system can be used for the connection member 17. When a solder material is used, the metal foils 10 ab, 10 bb and the heat-dissipating fins 40 can be strongly joined via the solder material to perform reflow processing.

The heat-dissipating fins 40 may be of a water-cooled system or an air-cooled system. If necessary, the heat-dissipating fins 40 may be directly, that is not via the connection member 17, joined by pressurization to the metal foils 10 ab, 10 bb, by clamping from the outside.

For example, a ceramic material containing at least any of silicon nitride (SiN), alumina (Al₂O₃), and aluminum nitride (AlN) can be used for the above-described insulating plates 10 aa, 10 ba.

For example, copper (Cu) or a metal containing copper (Cu) as the main component can be used for the metal foils 10 ab, 10 ac, 10 ad, 10 bb, and 10 bc and metal block bodies 31 and 32.

For example, a material containing copper (Cu), or aluminum (Al), or alloys thereof as the main component can be also used for the heat-dissipating fins 40.

For example, aluminum (Al) and gold (Au) can be used for the metal wire 20 w.

For example, any of silicone gel, an epoxy resin, a cyanate resin, and a silicone resin can be used as the sealing resin 50. If necessary, a filler material constituted by an inorganic material (boron nitride (BN), aluminum nitride (AlN), and silicon nitride (SiN)) may be contained in the resin.

The thickness of the insulating plates 10 aa, 10 ba is 0.2 mm to 0.7 mm, and the thickness of the metal foils 10 ab, 10 ac, 10 ad, 10 bb, and 10 bc is 0.2 mm to 1.0 mm.

By providing such thin insulating substrates 10A, 10B above and below the semiconductor element 20 and connecting the components, it is possible to conduct heat efficiently, which is generated from the semiconductor element 20 from the upper and lower main surfaces of the semiconductor element 20 to the upper and lower heat-dissipating fins 40 via the insulating substrate 10A and the insulating plate 10B.

Further, since metal block bodies 31, 32 are disposed above and below the semiconductor element 20 in the semiconductor device 2, heat generated from the semiconductor element 20 can be dissipated in the metal block bodies 31, 32.

Thus, in the semiconductor device 2, the upper and lower main electrodes of the semiconductor element 20 have good electrical connection to the metal foil 10 ac provided on the insulating substrate 10A and to the metal foil 10 bc provided on the insulating substrate 10B. At the same time, heat generated from the semiconductor element 20 can be efficiently dissipated in the metal block bodies 31, 32 and efficiently conducted from the upper and lower main surfaces of the semiconductor element 20 to the upper and lower heat-emitting fins 40 via the insulating substrate 10A and the insulating substrate 10B. As a result, reliability of the semiconductor device 2 can be increased. In particular, since the metal block bodies 31, 32 are disposed, heat generated from the semiconductor element 20 is not concentrated in parts of the insulating substrates 10A, 10B. Therefore, heat generated from the semiconductor element 20 can be efficiently conducted from almost the entire region of the insulating substrates 10A, 10B to the upper and lower heat-dissipating fins 40.

Thus, in the semiconductor device 2, a metal block body 31 is disposed between the collector electrode of the semiconductor element 20 and the metal foil 10 ac. Further, the metal plate 30 and the metal block body 32 are disposed between the emitter electrode of the semiconductor element 20 and the metal foil 10 bc.

If necessary, either of the metal block bodies 31, 32 may be omitted.

A semiconductor device carrying a plurality of semiconductor elements 20 can be also constituted following the example of the semiconductor device 2 shown in FIG. 10. For example, a semiconductor device of a 2 in 1 structure such as explained in the first embodiment can be also formed.

If necessary, a plurality of semiconductor devices 2 can be stacked with the heat-dissipating fins 40 being interposed therebetween, in the same manner as the semiconductor devices shown in FIG. 9 and described in the first embodiment. A lead-free solder layer of a tin (Sn)-silver (Ag) system, a lead-containing solder layer of a tin (Sn)-lead (Pb) system, or an electrically conductive compound can be used as the connection member that thermally connects the semiconductor devices 2 and heat-dissipating fins 40. A semiconductor device of a structure different from that of the semiconductor device 2 can be also stacked therewith, with the heat-dissipating fin 40 being interposed therebetween.

Third Embodiment

FIG. 11 is a schematic drawing illustrating a semiconductor device according to the third embodiment.

As shown in the figure, in a semiconductor device (semiconductor package) 3, a metal plate (die pad) 33A is used as a base body and at least one semiconductor element 20 is mounted on the metal plate 33A.

In this case, the semiconductor element 20 is the so-called power semiconductor element and, for example, corresponds to a RC-IGBT element. In addition to the RC-IGBT element, for example, a usual IGBT element, a power MOSFET, and a FWD element can be disposed as the semiconductor element 20.

In the semiconductor device 3, one main electrode (for example, a collector electrode) of the semiconductor element 20 is joined via a solder layer 11 to the metal plate 33A. A metal plate 30 that functions as a heat spreader or a lead frame is joined via a lead-free solder layer 12 to the other main electrode (for example, an emitter electrode), which is provided oh the main surface on the side opposite to that of the main surface where the aforementioned one main electrode (for example, the collector electrode) of the semiconductor element 20 is disposed. A control electrode (not shown in the figure) of the semiconductor element 20 that is separately provided on the surface side where the other main electrode (for example, the emitter electrode is disposed) and a metal plate 34 disposed apart from the metal plate 33A are electrically connected by means of a metal wire 20 w.

Further, in the semiconductor device 3, a separate metal plate (die pad) 33B that is a base body is disposed opposite to the metal plate 33A. The metal plate 30 and the metal plate 33B are joined via a lead-free solder layer 13.

The metal plates 33A, 33B, metal plate 30, and semiconductor element 20 are electrically and thermally connected to each other.

Further, in the semiconductor device 3, a sealing resin 50 is provided in a gap between the metal plates 33A, 33B and on the side surfaces thereof and also on the side surface and upper surface of the metal plate 34 with the object of protecting the metal plates 33A, 33B, 34, semiconductor element 20, and metal wire 20 w. The main surfaces of the metal plates 33A, 33B on the sides opposite to those of the main surfaces that face the semiconductor element 20 and also the lower surface of the metal plate 34 are exposed from the sealing resin 50 and exhibited, that is, not covered by the sealing resin 50.

In the semiconductor device 3, flat surfaces are formed by the main surfaces of the metal plates 33A, 33B on the sides opposite to those of the main surfaces that face the semiconductor element 20, the lower surface of the metal plate 34, and also main surfaces (surfaces along the broken lines A-B in the figure), which is constituted by parts of the sealing resin 50.

Insulating layers 10 ada, 10 adb are formed on the aforementioned flat surfaces by using an aerosol deposition (AD) method by which a starting material power is blown and deposited on a surface where the film is to be formed.

With the aerosol deposition method, first, aerosol in which particles are contained in a carrier gas is produced by causing a predetermined carrier gas to flow in a fluidized bed including particles that serve as a starting material for the insulating layers 10 ada, 10 adb. Then, the produced aerosol is blown onto the surface where the film is to be formed, that is, on the flat surface constituted by the metal plates 33A, 33B, 34 and part of the sealing resin 50 under a reduced pressure in a low-temperature environment, such as normal temperature environment. In this case, the particles colliding with the surface where the film is to be formed are crushed or deformed by the impact during collision and are deposited on the surface where the film is to be formed. Under the effect of collision energy, the particles strongly adhere to and are deposited on the surface where the film is to be formed and the film that has been heretofore formed on the surface where the film is to be formed.

For example, particles with a size of about 1 nm to 3 μm, preferably about 5 nm to 1 μm can be used for the particles serving as a starting material. By adjusting an aerosol blowing nozzle or pressure conditions, it is possible to accelerate the particles to a velocity of about several tens to several hundreds of meters per second, for example, from about 5 m/sec to 500 m/sec. As a result of collision with the surface where the film is to be formed, the particles are crushed and deformed to a side of about several tens of nanometers, for example, a side of about 0.5 nm to 50 nm. A film in which fragments of such a size are joined together, which contains no voids, and which has a dense nanostructure such that grain boundaries cannot be identified is formed on the surface.

By using such aerosol deposition method, it is possible to form flat insulating layers 10 ada, 10 adb that have good adhesion to the surface and dense nanostructure to a desired film thickness of about several micrometers to several hundreds of micrometers, for example, a thickness of 10 μm to 100 μm. Further, when the aerosol deposition method is used, the effect of residual stresses, which appears in substrates of sintered bodies, can be avoided.

Further, in the semiconductor device 3, a heat-dissipating fin 40 is thermally connected via a connection member 17 to the main surface of the insulating layer 10 ada on the side opposite to that of the main surface that faces the semiconductor element 20. A heat-dissipating fin 40 is also thermally connected via a connection member 17 to the main surface of the insulating layer 10 adb on the side opposite to that of the main surface that faces the semiconductor element 20. For example, an electrically conductive compound is used for the connection members 17 used herein. Heat-dissipating fins 40 may be of a water-cooled system or an air-cooled system. If necessary, heat-dissipating fins 40 may be directly, that is, not via the connection member 17, joined by pressurization to the insulating layers 10 ada, 10 adb, by clamping from the outside.

For example, a ceramic material containing at least any of silicon nitride (SiN), alumina (Al₂O₃), aluminum nitride (AlN), and boron nitride (BN) can be used for the above-described insulating layers 10 ada, 10 adb. When the insulating layers 10 ada, 10 adb are formed using the aerosol deposition method, ceramic particles of these materials can be used.

For example, copper (Cu) or a metal containing copper (Cu) as the main component can be used for the metal plates 33A, 33B, and 34.

For example, a material containing copper (Cu), or aluminum (Al), or alloys thereof as the main component can be also used for heat-dissipating fin 40.

For example, aluminum (Al) and gold (Au) can be used for the metal wire 20 w.

For example, any of silicone gel, an epoxy resin, a cyanate resin, and a silicone resin can be used as the sealing resin 50. If necessary, a filler material constituted by an inorganic material (boron nitride (BN), aluminum nitride (AlN), and silicon nitride (SiN)) may be contained in the resin.

Thus, the semiconductor device 3 is provided with at least one semiconductor element having a main electrode and another main electrode provided on the side opposite to that of the aforementioned main electrode, the metal plate 33A joined to the main electrode, and the metal plate 33 b electrically connected to the other main electrode. Further, the insulating layer 10 ada is formed on the surface of the metal plate 33A that is opposite to the surface joined to the main electrode, and the insulating layer 10 adb is formed on the surface of the metal plate 33B that is opposite to the surface electrically connected to the other main electrode.

By disposing such metal plates 33A, 33B above and below the semiconductor element 20, it is possible to efficiently conduct the heat generated from the semiconductor element 20 from the upper and lower main surfaces of the semiconductor element 20 to the upper and lower heat-dissipating fins 40 via the metal plate 33A and the metal plate 33B.

Thus, in the semiconductor device 3, the upper and lower main electrodes of the semiconductor element 20 have good electrical connection to the metal plates 33A, 33B, and heat generated from the semiconductor element 20 can be efficiently dissipated in the metal plates 33A, 33B and be efficiently conducted from the upper and lower main surfaces of the semiconductor element 20 to the upper and lower heat-emitting fins 40. As a result, reliability of the semiconductor device 3 can be increased.

In particular, where the insulating layers 10 ada, 10 adb are formed by the aerosol deposition method so as to have small thickness, high density and good adhesion to the metal plates 33A, 33B, thermal resistance in the insulating layers 10 ada, 10 adb can be inhibited while ensuring high insulating ability and heat generated from the semiconductor element 20 can be efficiently conducted to the upper and lower heat-dissipating fins 40.

For example, when substrates from ceramic sintered bodies are used for portions of the insulating layers 10 ada, 10 adb, substrates with a thickness of 0.2 mm to 0.7 mm can be used with consideration for insulating capacity and breakdown voltage. By contrasts, when ceramic layers are formed using the aerosol deposition method in portions of the insulating layers 10 ada, 10 adb, since the ceramic layers can be formed to have a dense structure containing no voids or the like, the insulating capacity is increased by a factor of about 10. In other words, when ceramic layers are formed using the aerosol deposition method, the thickness can be reduced to about 1/10 that of the semiconductor sintered body substrate while ensuring similar insulating capacity. Therefore, a contribution is made to the reduction of thickness and the miniaturization of the semiconductor device 3.

Further, the ceramic layer formed by using the aerosol deposition method has thermal conductivity similar to that of the bulk body. Thus, it is possible to ensure thermal conductivity of about 80 W/m·K with silicon nitride (SiN), about 20 W/m·K with alumina (Al₂O₃), and about 160 W/m·K to about 180 W/m·K with aluminum nitride (AlN). As described hereinabove, the semiconductor layer formed using the aerosol deposition method can be formed to a smaller thickness due to the production method thereof and insulating capacity. Therefore, thermal resistance of the ceramic layer can be reduced. Therefore, when the insulating layers 10 ada, 10 adb are formed using the aerosol deposition method, thermal conduction to heat-dissipating fins 40 can be ensured without forming metal foils on the surfaces of the insulating layers 10 ada, 10 adb that are on the side opposite to that of the metal plates 33A, 33B.

Furthermore, when the aerosol deposition method is thus used, since an insulating layer such as a ceramic layer can be deposited on the surface where the film is to be formed (flat surface), which is obtained after the sealing resin 50 has been formed, it is not necessary to prepare the insulating plates 10 aa, 10 ba of a predetermined size in advance and form the insulating substrates 10A, 10B provided with the predetermined metal foils by using the prepared insulating plates. As a result, the manufacturing process can be simplified and cost can be reduced.

For example, an insulating layer can be formed in the following manner by the aerosol deposition method.

FIG. 12 is an explanatory drawing illustrating an example of the insulating layer formation process using the aerosol deposition method. FIG. 13 is an explanatory drawing illustrating another example of the insulating layer formation process using the aerosol deposition method.

For example, first, the semiconductor element 20 and the metal wire 20 w are sealed with the synthetic resin 50, and the predetermined main surfaces of the metal plates 33A, 33B, and 34 being left uncovered. Then, as shown in FIG. 12, an aerosol containing predetermined particles is blown from nozzles 61, 62 respectively onto the surface where the metal plates 33A, 34 are exposed from the synthetic resin 50 and the surface where the metal plate 33B is exposed from the synthetic resin 50. By moving the nozzles 61, 62 according to the predetermined drawing pattern, it is possible to blow the aerosol so as to form the insulating layers selectively in the desired regions. Further, the aerosol can be prevented from adhering to the unnecessary portions by disposing the metal masks 63, 64 opposite to the surface where the metal plates 33A, 34 are exposed from the synthetic resin 50 and the surface where the metal plate 33B is exposed from the synthetic resin 50. As a result, the insulating layers can be formed simultaneously on both surfaces where the synthetic resin 50 has been formed.

Further, with the mode of conducting aerosol deposition after the synthetic resin 50 has been formed, the insulating layers can be also formed as shown in FIG. 13. For example, after the synthetic resin 50 has been formed, a configuration is sometimes obtained such that a plurality of structural bodies 70 in which external connection terminals 71, 72, which have been pulled out of the synthetic resin 50, are connected to a tie bar 73. In the case of such a configuration, an aerosol containing predetermined particles is also blown from the nozzles 61, 62 onto both surfaces of each structural body 70. By moving the nozzles 61, 62 according to the predetermined drawing pattern, it is possible to blow the aerosol so as to form the insulating layers selectively in the desired regions. Further, the aerosol can be prevented from adhering to the unnecessary portions by disposing metal masks 63, 64 opposite to the surface where the metal plates 33A, 34 are exposed from the sealing resin 50 and the surface where the metal plate 33B is exposed from the sealing resin 50. As a result, the insulating layers can be formed simultaneously on both surfaces where the sealing resin 50 has been formed. Such blowing from the nozzles 61, 62 onto the structural bodies 70 may be conducted successively and continuously with respect to a plurality of structural bodies 70 and insulating layers may be formed on both surfaces of all of the structural bodies 70 that have been connected to the tie bar 73. In FIG. 13, the control terminals are omitted.

FIG. 12 and FIG. 13 illustrate the case in which the aerosol is blown from two opposing nozzles and the insulating layers are formed on both surface that are the objects of film formation, but it goes without saying that the insulating layers can be also formed on each surface by using one nozzle.

A semiconductor device carrying a plurality of semiconductor elements 20 can be also constituted following the example of the semiconductor device 3 shown in FIG. 11. For example, a semiconductor device of a 2 in 1 structure such as explained in the first embodiment can be also formed.

If necessary, a plurality of semiconductor devices 3 can be stacked, with the heat-dissipating fins 40 being interposed therebetween, in the same manner as the semiconductor devices shown in FIG. 9 and described in the first embodiment. In this case, an electrically conductive compound can be used as the connection member that thermally connects the semiconductor devices 3 and heat-dissipating fins 40. A semiconductor device of a structure different from that of the semiconductor device 3 can be also stacked therewith the heat-dissipating fin 40 being interposed therebetween.

Fourth Embodiment

FIG. 14 is a schematic drawing illustrating a semiconductor device according to the fourth embodiment.

In a semiconductor device 4 according to the fourth embodiment, a metal foil 10 ac of an insulating substrate 10A is provided as far as the vicinity of the end portion (portion C in the figure) of an insulating plate 10 aa.

Further, in the semiconductor device 4, an insulating plate 10 ga is provided separately, a control terminal 10 g is connected to the upper surface side of the insulating plate 10 ga, and a metal foil 10 gb is connected to the lower surface side of the insulating plate 10 ga. The metal foil 10 gb is joined to the end portion of the metal foil 10 ac via a solder layer 16. The control terminal 10 g and the metal foil 10 gb can be formed for example by the DCB method.

With such an arrangement of the control terminal 10 g and the like, the metal foil 10 ac on the insulating plate 10 aa can be provided as far as the vicinity of the end portion of the insulating plate 10 aa, and the control terminal 10 g and a control electrode of the semiconductor element 20 can be reliably electrically connected by means of a metal wire 20 w. By extending the metal foil 10 ac close to the end portion of the insulating plate 10 aa, it is possible to dissipate heat efficiently, which is generated from the semiconductor element 20 also in the stretched portion (portion C in the figure) of the metal foil 10 ac, and heat dissipation effect can be increased.

Thus, in the semiconductor device 4, good electrical connection can be realized on the upper and lower main surfaces of the semiconductor element 20 and heat dissipation can be efficiently conducted from the upper and lower main surfaces of the semiconductor element 20 and also from the upper and lower main surfaces of the semiconductor device 4 carrying the semiconductor element 20.

The insulating substrate 10A, control terminal 10 g, insulating plate 10 ga, and metal foil 10 gb of such a structure may be applied to the semiconductor device 2 described in the second embodiment and also to the semiconductor device 3 described in the third embodiment. In the semiconductor device 3 described in the third embodiment, the metal plate 33A may be extended as far as the vicinity of the side surface of the sealing resin 50 and, as shown in FIG. 14, the control terminal 10 g, insulating plate 10 ga, and metal foil 10 gb may be disposed on the metal plate 33A. As a result, electrical connection of the control terminal 10 g and the control electrode can be reliably performed, and heat dissipation effect attained with the semiconductor devices 2 and 3 described in the second and third embodiments can be further increased.

Fifth Embodiment

FIG. 15 is a schematic drawing illustrating a semiconductor device according to the fifth embodiment.

In a semiconductor device 5 according to the fifth embodiment, a metal foil 10 ac of an insulating substrate 10A is provided as far as the vicinity of the end portion (portion C in the figure) of an insulating plate 10 aa. Further, an end portion of a control terminal 10 g can be joined by any method such as laser welding, soldering, ultrasonic joining, and direct joining by heating under pressure to a control electrode that has been separately provided on an arrangement surface side of one main electrode (for example, an emitter electrode) of a semiconductor element 20.

With such an arrangement of the control terminal 10 g and the like, the metal foil 10 ac located on the insulating plate 10 aa can be provided as far as the vicinity of the end portion of the insulating plate 10 aa, and the control terminal 10 g and the control electrode of the semiconductor element 20 can be reliably electrically connected in a wireless manner. By extending the metal foil 10 ac close to the end portion of the insulating plate 10 aa, it is possible to dissipate heat efficiently, which is generated from the semiconductor element 20 also in the stretched portion (portion C in the figure) of the metal foil 10 ac, and heat dissipation effect can be increased.

Thus, in the semiconductor device 5, good electrical connection can be realized on the upper and lower main surfaces of the semiconductor element 20, and heat dissipation can be efficiently conducted from the upper and lower main surfaces of the semiconductor element 20 and also from the upper and lower main surfaces of the semiconductor device 5 carrying the semiconductor element 20.

Such connection of the control terminal 10 g and the control electrode may be also applied to the semiconductor device 2 described in the second embodiment and the semiconductor device 3 described in the third embodiment. As a result, the electrically connection of the control terminal 10 g and the control electrode can be reliably performed and heat dissipation effect of the semiconductor devices 2, 3 such as described in the second and third embodiments can be further improved.

In the explanation above, the case is described in which heat-dissipating fins are disposed on the upper and lower surface sides of the semiconductor device, but the same effect as described above can be also obtained with the semiconductor device in which a heat-dissipating fin is disposed on at least one of the upper and surface and lower surface.

The principle of the present invention is described in a simple manner. A large number of modifications and variations can be introduced by a person skilled in the art, the present invention is not limited to the above-described precise configurations and examples of applications, and all the corresponding variation examples and equivalents are assumed to be included into the scope of the present invention defined by the appended claims and equivalents thereof. 

1. A semiconductor device comprising: a first substrate having a first insulating plate, a first metal foil having a portion provided in a region on an inner side from ends of a first main surface of the first insulating plate, and a second metal foil having a portion provided in a region on an inner side from ends of a second main surface of the first insulating plate; a second substrate having a second insulating plate, a third metal foil having a portion provided in a region on an inner side from ends of a first main surface of the second insulating plate, which is disposed so as to face the first metal foil, and a fourth metal foil having a portion provided in a region on an inner side from ends of a second main surface of the second insulating plate; and a semiconductor element disposed between the first substrate and the second substrate, and having a first main electrode electrically connected to the first metal foil and a second main electrode electrically connected to the third metal foil; and a sealing resin that seals the semiconductor element, wherein the sealing resin covers side surfaces and end surfaces of the first insulating plate on an outer side from the first metal foil and second metal foil, side surfaces and end surfaces of the second insulating plate on the outer side from the third metal foil and fourth metal foil, and side surfaces of the second metal foil and fourth metal foil, and a main surface of the second metal foil, which is on the side opposite to that of the first insulating plate, and a main surface of the fourth metal foil, which is on the side opposite to that of the second insulating plate, are exposed without the sealing resin.
 2. A semiconductor device according to claim 1, wherein a metal member is disposed at least either between the first main electrode and the first metal foil or between the second main electrode and the third metal foil.
 3. A semiconductor device according to claim 1, wherein at least one of the second metal foil and the fourth metal foil is thermally connected to a heat dissipating body.
 4. A semiconductor device according to claim 3, wherein another semiconductor device is thermally connected to the heat dissipating body.
 5. A semiconductor device according to claim 1, further comprising a terminal electrically connected to the semiconductor element and led out to the outside of the sealing resin.
 6. A semiconductor device according to claim 5, further comprising: a third insulating plate; and a fifth metal foil provided on a first main surface of the third insulating plate and electrically connected to the first metal foil, wherein the terminal is connected to a second main surface of the third insulating plate and electrically connected by a wire to the semiconductor element.
 7. A semiconductor device comprising: a first metal plate; a second metal plate disposed opposite to the first metal plate; a semiconductor element disposed between the first and the second metal plates and electrically connected to the first metal plate and the second metal plate; a first deposited layer with insulating properties formed on a main surface of the first metal plate, which is on a side opposite to that of the semiconductor element; and a second deposited layer with insulating properties formed on a main surface of the second metal plate, which is on a side opposite to that of the semiconductor element.
 8. A semiconductor device according to claim 7, further comprising a sealing resin that seals the semiconductor element, wherein the sealing resin covers side surfaces of the first metal plate and the second metal plate, the first deposited layer is formed on a main surface of the first metal plate, which is on a side opposite to that of the semiconductor element and on the sealing resin that covers a side surface of the first metal plate, and the second deposited layer is formed on a main surface of the second metal plate on a side opposite to that of the semiconductor element, and on the sealing resin that covers a side surface of the second metal plate.
 9. A semiconductor device according to claim 7, wherein a heat dissipating body is thermally connected to at least one of the first deposited layer and the second deposited layer.
 10. A semiconductor device according to claim 9, wherein another semiconductor device is thermally connected to the heat dissipating body.
 11. A method for manufacturing a semiconductor device, comprising: a step of forming a first substrate by providing a first metal foil and a second metal foil on one main surface of a first insulating plate; a step of facing a first main electrode, provided on one main surface of a first semiconductor element, to the first metal foil, and electrically connecting the first main electrode and the first metal foil; a step of facing a second main electrode, provided on one main surface of a second semiconductor element, to the second metal foil, and electrically connecting the second main electrode and the second metal foil; a step of forming a second substrate by providing a third metal foil and a fourth metal foil on one main surface of a second insulating plate; and steps of facing a surface side of the second substrate, where the third metal foil and the fourth metal foil are provided, to a surface side of the first substrate, where the first semiconductor element and the second semiconductor element are disposed; electrically connecting the third metal foil and a third main electrode provided on a main surface of the first semiconductor element, which is on a side opposite to that of the main surface where the first main electrode is provided; and electrically connecting the fourth metal foil and a fourth main electrode provided on a main surface of the second semiconductor element, which is on a side opposite to that of the main surface where the second main electrode is provided.
 12. A method for manufacturing a semiconductor device according to claim 11, further comprising a step of electrically connecting the third main electrode and the second metal foil by using a metal member before facing the first substrate and the second substrate to each other.
 13. A method for manufacturing a semiconductor device according to claim 11, wherein the first substrate has a fifth metal foil provided on a main surface of the first insulating plate, which is on a side opposite to those of the first metal foil and the second metal foil; the second substrate has a sixth metal foil provided on a main surface of the second insulating plate, which is on a side opposite to those of the third metal foil and the fourth metal foil, and wherein the method for manufacturing a semiconductor device further comprises, after the step of electrically connecting the third main electrode and the third metal foil and electrically connecting the fourth main electrode and the fourth metal foil, a step of sealing the first semiconductor element and the second semiconductor element and a step of sealing the first insulating plate and the second insulating plates, by using a sealing resin while a main surface of the fifth metal foil, which is on a side opposite to that of the first insulating plate, and a main surface of the sixth metal foil, which is on a side opposite to that of the second insulating plate, are exposed.
 14. A method for manufacturing a semiconductor device, comprising: a step of forming a first substrate by providing a first metal foil and a second metal foil on one main surface of a first insulating plate; a step of facing a first main electrode, provided on one main surface of a first semiconductor element, to the first metal foil, and electrically connecting the first main electrode and the first metal foil; a step of forming a second substrate by providing a third metal foil on one main surface of a second insulating plate; a step of facing a second main electrode, provided on one main surface of a second semiconductor element, to the third metal foil, and electrically connecting the second main electrode and the third metal foil; and steps of facing a surface side of the second substrate, where the second semiconductor element is disposed, to a surface side of the first substrate, where the first semiconductor element is disposed; electrically connecting the third metal foil and a third main electrode provided on a main surface of the first semiconductor element, which is on the side opposite to that of the main surface where the first main electrode is provided; and electrically connecting the second metal foil and a fourth main electrode provided on a main surface of the second semiconductor element, which is on a side opposite to that of the main surface where the second main electrode is provided.
 15. A method for manufacturing a semiconductor device according to claim 14, wherein the first substrate has a fourth metal foil provided on a main surface of the first insulating plate, which is on a side opposite to that of the first metal foil and the second metal foil; the second substrate has a fifth metal foil provided on a main surface of the second insulating plate, which is on a side opposite to that of the third metal foil, and wherein the method for manufacturing a semiconductor device further comprises, after the step of electrically connecting the third main electrode and the third metal foil and electrically connecting the fourth main electrode and the second metal foil, a step of sealing the first semiconductor element and the second semiconductor element and the first insulating plate and the second insulating plate by using a sealing resin while a main surface of the fourth metal foil, which is on a side opposite to that of the first insulating plate, and a main surface of the fifth metal foil, which is on a side opposite to that of the second insulating plate, are exposed.
 16. A method for manufacturing a semiconductor device, comprising: a step of forming a substrate by providing a first metal foil on one main surface of a first insulating plate; a step of facing a first main electrode, provided on one main surface of a first semiconductor element, to face the first metal foil, and electrically connecting the first main electrode and the first metal foil; a step of facing a second main electrode, provided on one main surface of a second semiconductor element, to the first metal foil, and electrically connecting the second main electrode and the first metal foil; a step of forming a second substrate by providing a second metal foil on one main surface of a second insulating plate; and steps of facing a surface side of the second substrate, where the second metal foil is provided, to a surface side of the first substrate, where the first and second semiconductor elements are disposed; and electrically connecting by using the second metal foil, a third main electrode, which is provided on a main surface of the first semiconductor element on a side opposite to that of the main surface where the first main electrode is provided, and a fourth main electrode, which is provided on a main surface of the second semiconductor element on a side opposite to that of the main surface where the second main electrode is provided. 